1. Field of the Invention
The present invention relates to a secondary air supply system that supplies secondary air to an engine and a vehicle including the same.
2. Description of the Background Art
Conventionally, a technique for supplying secondary air to an exhaust pipe has been developed in order to purify an exhaust gas exhausted from a vehicle (see JP 2006-183513 A, for example).
In a secondary air introduction device described in JP 2006-183513 A, a first tube and a second tube are connected to the exhaust pipe. Secondary air is supplied to the exhaust pipe through the first and second tubes. This causes the exhaust gas in the exhaust pipe to be oxidized, resulting in purification of the exhaust gas.
In a vehicle such as a motorcycle, purification of the exhaust gas using a catalyst device is performed in addition to the purification of the exhaust gas using the secondary air. When an amount of the secondary air supplied to the exhaust pipe increases, however, an amount of oxygen flowing into the catalyst device increases, resulting in lower purification efficiency of the catalyst device. Therefore, it is difficult to effectively improve the efficiency of purifying the exhaust gas simply by providing the foregoing secondary air introduction device and catalyst device in the exhaust pipe.